Why rehabilitation research does not work (as well as we think it should)

Establishing treatment effectiveness is a high priority for rehabilitation research. The use of traditional quantitative null hypotheses to achieve this priority is reviewed. Three problems are identified in the analysis and interpretation of investigations based on statistical testing of hypotheses: (1) confusion of clinical and statistical significance, (2) low statistical power in detecting clinically important results, and (3) a failure to understand the importance of replication in developing a knowledge base for rehabilitation practice. Technical aspects associated with each problem are reviewed and examples presented illustrating the impact of low statistical power and the results of misinterpreting statistical significance tests. Several specific recommendations are made to improve the clinical usefulness of quantitative research conducted in rehabilitation.